This May 29, 2016, image of a target called "Private Joseph Field" combines images from the microscopic imager on NASA's Mars Exploration Rover Opportunity with enhanced color information from the rover's panoramic camera. The target is on the western rim of Mars' Endeavour Crater.

This rock, dubbed "Gasconade," was investigated by NASA's Mars Exploration Rover Opportunity while the rover was perched on "Spirit Mound" at the western edge of Mars' Endeavour Crater. Four Oct. 2, 2016, frames from Opportunity's microscopic imager are joined in this mosaic view.

This Dec. 2, 2016, view from the Navigation Camera (Navcam) on the mast of NASA's Curiosity Mars Rover shows rocky ground within view while the rover was working at an intended drilling site called "Precipice" on lower Mount Sharp.

A NASA radio on Europe's Trace Gas Orbiter, which reached Mars in October 2016, has succeeded in its first test of receiving data from NASA Mars rovers, both Opportunity and Curiosity. This graphic depicts the geometry of the relay from Opportunity to the orbiter, which then sent the data to Earth.

Diagonal striping on this map of a portion of Mars' Utopia Planitia region indicates the area where a large subsurface deposit rich in water ice was assessed using the Shallow Radar (SHARAD) instrument on NASA's Mars Reconnaissance Orbiter. The deposit holds about as much water as Lake Superior.

These two images show Shallow Radar (SHARAD) instrument data from two tracks in a part of Mars' Utopia Planitia region where the orbiting, ground-penetrating radar on NASA's Mars Reconnaissance Orbiter detected subsurface deposits rich in water ice.

This vertically exaggerated view shows scalloped depressions in a part of Mars where such textures prompted researchers to check for buried ice, using ground-penetrating radar aboard NASA's Mars Reconnaissance Orbiter. They found about as much frozen water as the volume of Lake Superior.

On Nov. 1, 2016, the HiRISE camera on NASA's Mars Reconnaissance Orbiter observed the impact site of Europe's Schiaparelli test lander, gaining the first color view of the site since the lander's Oct. 19 arrival. These cutouts cover locations where three parts of the spacecraft reached the ground.

The dark, smooth-surfaced rock at the center of this Oct. 30, 2016, image from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover was examined with laser pulses and confirmed to be an iron-nickel meteorite. It is about the size of a golf ball.

The dark, golf-ball-size object in this composite, colorized view from the ChemCam instrument on NASA's Curiosity Mars rover is a nickel-iron meteorite, as confirmed by analysis using laser pulses from ChemCam on Oct. 30, 2016. The grid of bright spots on the rock resulted from the laser pulses.

This Oct. 25, 2016, image from the HiRISE camera on NASA's Mars Reconnaissance Orbiter shows the area where the Europe's Schiaparelli test lander struck Mars, with magnified insets of three sites where spacecraft components hit the ground. It adds detail not seen in earlier imaging of the site.

This comparison of before-and-after images shows two spots that likely appeared in connection with the Oct. 19, 2016, Mars arrival of the European Space Agency's Schiaparelli test lander. The images are from the Context Camera on NASA's Mars Reconnaissance Orbiter.

This image shows spidery channels eroded into Martian ground. It is a Sept. 12, 2016, example from HiRISE camera high-resolution observations of more than 20 places that were chosen in 2016 on the basis of about 10,000 volunteers' examination of Context Camera lower-resolution views of larger areas.

This artist's concept from the European Space Agency depicts the Trace Gas Orbiter and its entry, descent and landing demonstrator module, Schiaparelli, approaching Mars. The separation occurred on Oct. 16, 2016. The orbiter and the lander are components of the ExoMars 2016 mission of ESA and Roscosmos.

This map show a portion of Endeavour Crater's western rim that includes
the "Marathon Valley" area investigated intensively by NASA's Mars Exploration Rover Opportunity in 2015 and 2016, and a fluid-carved gully that is a destination to the south for the mission.

This stereo scene from NASA's Mars Exploration Rover Opportunity shows "Spirit Mound" overlooking the floor of Endeavour Crater. The view appears three-dimensional when seen through blue-red glasses with the red lens on the left.

This Sept. 21, 2016, scene from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity shows "Spirit Mound" overlooking the floor of Endeavour Crater. The mound stands near the eastern end of "Bitterroot Valley" on the western rim of the crater, and this view faces eastward.

This Sept. 21, 2016, scene from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity shows "Spirit Mound" overlooking the floor of Endeavour Crater. The mound stands near the eastern end of "Bitterroot Valley" on the western rim of the crater, and this view faces eastward.

This scene from NASA's Mars rover Opportunity shows "Wharton Ridge," on the western rim of Endeavour Crater. The ridge's name honors the memory of astrobiologist Robert A. Wharton (1951-2012). The scene is presented in enhanced color to make differences in surface materials more easily visible.

This scene from NASA's Mars rover Opportunity shows "Wharton Ridge," which forms part of the southern wall of "Marathon Valley" on the rim of Endeavour Crater. The ridge's name honors the memory of astrobiologist Robert A. Wharton (1951-2012). The scene is presented in approximately true color.

This graphic indicates a similarity between 2016 (dark blue line) and five past years in which Mars has experienced global dust storms (orange lines and band), compared to years with no global dust storm (blue-green lines and band). The horizontal scale is time-of-year on Mars

Two 2001 images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance when haze raised by dust-storm activity in the south became globally distributed. The images were taken about a month apart.

This September 2016 self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Quela" drilling location in the scenic "Murray Buttes" area on lower Mount Sharp. The panorama was stitched together from multiple images taken by the MAHLI camera at the end of the rover's arm.

This 360-degree panorama was acquired on Sept. 4, 2016, by the Mast Camera on NASA's Curiosity Mars rover while the rover was in a scenic area called "Murray Buttes" on lower Mount Sharp. The flat-topped mesa near the center of the scene rises to about 39 feet above the surrounding plain.

This map shows the route driven by NASA's Curiosity Mars rover from the location where it landed in August 2012 to its location in September 2016 at "Murray Buttes," and the path planned for reaching destinations at "Hematite Unit" and "Clay Unit" on lower Mount Sharp.

This graphic maps locations of the sites where NASA's Curiosity Mars rover collected its first 18 rock or soil samples for laboratory analysis inside the vehicle. It also presents images of the drilled holes where 14 rock-powder samples were acquired, most recently at "Quela," on Sept. 18, 2016.

The top of the butte in this Sept. 1, 2016, scene from the Mast Camera (Mastcam) on NASA's Curiosity Mars rover stands about 16 feet above the rover and about 82 feet east-southeast of the rover. The site is in the "Murray Buttes" area of lower Mount Sharp, and this particular butte is called "M9a."

The mesa in the center of this scene from the "Murray Buttes" area on Mars is longer than a football field. The panorama combines images taken by the Mastcam on NASA's Curiosity Mars rover on Aug. 22 and Aug. 23, 2016.

The two prominent mesas in this Aug. 18, 2016, view of Mars' "Murray Buttes" region from the Curiosity Mars rover's Mastcam are about 260 feet (about 80 meters) apart. The one on the right is about 33 feet high, and its top is about 270 feet from the rover's position when the images were taken.

Apollo 11 astronaut Buzz Aldrin, left, and Erisa Hines of NASA's Jet Propulsion Laboratory in Pasadena, California, speak to members of the news media during a preview of the new "Destination: Mars" experience at the Kennedy Space Center visitor complex in Florida.

This map of an area within the Arabia Terra region on Mars shows where hydrologic modeling predicts locations of depressions that would have been lakes (black), overlaid with a map of the preserved valleys (blue lines, with width exaggerated for recognition) that would have been streams.

Streamlined forms in this Martian valley resulted from the outflow of a lake hundreds of millions years more recently than an era of Martian lakes previously confirmed. This image from the Context Camera on NASA's Mars Reconnaissance Orbiter covers an area in Arabia Terra about 8 miles wide.

This 360-degree vista was acquired on Aug. 5, 2016, by the Mastcam on NASA's Curiosity Mars rover as the rover neared features called "Murray Buttes" on lower Mount Sharp. The dark, flat-topped mesa seen to the left of the rover's arm is about 50 feet high and, near the top, about 200 feet wide.

This July 22, 2016, stereo scene from the Mastcam on NASA's Curiosity Mars Rover shows boulders at a site called "Bimbe" on lower Mount Sharp. They contain pebble-size and larger rock fragments. The image appears three dimensional when viewed through red-blue glasses with the red lens on the left.

This 360-degree vista was acquired on Aug. 5, 2016, by the Mastcam on NASA's Curiosity Mars rover as the rover neared features called "Murray Buttes" on lower Mount Sharp. The dark, flat-topped mesa seen to the left of the rover's arm is about 50 feet high and, near the top, about 200 feet wide.

NASA's Curiosity Mars rover began close-up investigation of a target called "Marimba," on lower Mount Sharp, during the week preceding the fourth anniversary of the mission's Aug. 6, 2016, landing. Curiosity's Navigation Camera took this shot of the rover's arm over Marimba on Aug. 2, 2016.

This is a shareable image about a social media game called Mars Rover. On their mobile devices, players drive a rover through rough Martian terrain, challenging themselves to navigate and balance the rover while earning points along the way.

This is a shareable animation about a social media game called Mars Rover. On their mobile devices, players drive a rover through rough Martian terrain, challenging themselves to navigate and balance the rover while earning points along the way.

Martian gullies as seen from HiRISE on NASA's Mars Reconnaissance Orbiter resemble gullies on Earth that are carved by liquid water. However, when they are observed with the addition of mineralogical information from CRISM, no evidence for alteration by water appears.

Martian gullies as seen in the top image from HiRISE on NASA's Mars Reconnaissance Orbiter resemble gullies on Earth that are carved by liquid water. However, when they are observed with the addition of mineralogical information from CRISM (bottom), no evidence for alteration by water appears.

NASA's Curiosity Mars rover autonomously selects some targets for the laser and telescopic camera of its ChemCam instrument. For example, on-board software analyzed the Navcam image at left, chose the target indicated with a yellow dot, and pointed ChemCam for laser shots and the image at right.

The MOXIE investigation on NASA's Mars 2020 rover will extract oxygen from the Martian atmosphere. In this image, MOXIE Principal Investigator Michael Hecht, of the Massachusetts Institute of Technology, Cambridge, is in the MOXIE laboratory at NASA's Jet Propulsion Laboratory, Pasadena, California.

This 2016 image comes from computer-assisted-design work on NASA's 2020 Mars rover. The design leverages many successful features of NASA's Curiosity rover, which landed on Mars in 2012, but it adds new science instruments and a sampling system to carry out the new goals for the 2020 mission

NASA's Mars 2020 Project will re-use the basic engineering of NASA's Mars Science Laboratory/Curiosity to send a different rover to Mars, with new objectives and instruments. This view depicts the top of the 2020 rover's mast.

This map shows the frequency of carbon dioxide frost's presence at sunrise on Mars, as a percentage of days year-round. Carbon dioxide ice more often covers the ground at night in some mid-latitude regions than in polar regions, where it is generally absent for much of summer and fall.

The white arrows indicate locations in this scene where numerous seasonal dark streaks, called "recurring slope lineae," have been identified in the Coprates Montes area of Mars' Valles Marineris by repeated observations from orbit.

Blue dots on this map indicate sites of recurring slope lineae (RSL) in part of the Valles Marineris canyon network on Mars. RSL are seasonal dark streaks that may be indicators of liquid water. The area mapped here has the highest density of known RSL on Mars.

Two sizes of ripples are evident in this Dec. 13, 2015, view of a top of a Martian sand dune, from NASA's Curiosity Mars rover. Sand dunes and the smaller type of ripples also exist on Earth. The larger ripples are a type not seen on Earth nor previously recognized as a distinct type on Mars.

This scene shows NASA's Curiosity Mars rover at a location called "Windjana," where the rover found rocks containing manganese-oxide minerals, which require abundant water and strongly oxidizing conditions to form.

"Marathon Valley" on Mars opens northeastward in this stereo version of a scene from the Pancam of NASA's Mars Exploration Rover Opportunity. The scene, recorded in April and May 2016, appears three-dimensional when seen through blue-red glasses with the red lens on the left.

"Marathon Valley" on Mars opens to a view across Endeavour Crater in this enhanced-color version of a scene from the Pancam of NASA's Mars Exploration Rover Opportunity. The scene merges many exposures taken during April and May 2016. The foreground shows the fractured texture of the valley.

"Marathon Valley" on Mars opens to a view across Endeavour Crater in this scene from the Pancam of NASA's Mars rover Opportunity. The scene merges many exposures taken during April and May 2016. The view spans from north (left) to west-southwest. Its foreground shows the valley's fractured texture.

This graphic maps the first 14 sites where NASA's Curiosity Mars rover collected rock or soil samples for analysis using the rover's onboard laboratory. It also presents images of the drilled holes where 12 rock-powder samples were acquired. At the other two sites Curiosity scooped soil samples.

The top of the rover's mast faces away in this May 11, 2016, self-portrait of NASA's Curiosity Mars rover, which shows the vehicle at the "Okoruso" drilling site on lower Mount Sharp. The scene is a mosaic of multiple images taken with the arm-mounted Mars Hands Lens Imager (MAHLI).7856

This May 11, 2016, self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Okoruso" drilling site on lower Mount Sharp's "Naukluft Plateau." The scene is a mosaic of multiple images taken with the arm-mounted Mars Hands Lens Imager (MAHLI).

This animated image blinks two versions of a May 11, 2016, selfie of NASA's Curiosity Mars rover at a drilled sample site called "Okoruso." In one version, cameras atop the rover's mast face the arm-mounted camera taking the portrait. In the other, they face away.

This graphic presents Martian atmospheric temperature data as curtains over an image of Mars taken during a regional dust storm. The temperature profiles extend from the surface to about 50 miles up. Temperatures are color coded, from minus 243 degrees Fahrenheit (purple) to minus 9 F (red).

NASA's Curiosity Mars rover measures the concentration of methane in the atmosphere at Gale Crater. A one-time spike in methane, up to about 7 parts per billion occurred during Curiosity's first Martian year. Variations in much lower background levels of methane may be seasonal.

By monitoring weather through two Martian years since landing in Gale Crater, NASA's Curiosity Mars rover has documented seasonal patterns in variables such as temperature, water-vapor content and air pressure. Each Mars year lasts nearly two Earth years.

By monitoring weather through two Martian years since landing in Gale Crater, NASA's Curiosity Mars rover has documented seasonal patterns in variables such as temperature, water-vapor content and air pressure. Each Mars year lasts nearly two Earth years.

This graphic illustrates where Mars mineral-mapping from orbit has detected minerals that can indicate where a volcano erupted beneath an ice sheet. The site is far from any ice sheet on modern Mars, in an area where unusual shapes have been interpreted as a possible result of volcanism under ice.

This early-morning view from the Mastcam on NASA's Curiosity Mars rover on March 16, 2016, covers a portion of the inner wall of Gale Crater. At right, the image fades into glare of the rising sun. Details such as gullies and debris fans help geologists understand processes that shaped the crater.